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virtio_net: introduce mergeable_xdp_get_buf()

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Separating the logic of preparation for xdp from receive_mergeable.

The purpose of this is to simplify the logic of execution of XDP.

The main logic here is that when headroom is insufficient, we need to
allocate a new page and calculate offset. It should be noted that if
there is new page, the variable page will refer to the new page.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Xuan Zhuo 2023-05-08 14:14:04 +08:00 committed by Jakub Kicinski
parent 363d8ce4b9
commit ad4858beb8
1 changed files with 79 additions and 56 deletions
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135
drivers/net/virtio_net.c
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@ -1166,6 +1166,81 @@ static int virtnet_build_xdp_buff_mrg(struct net_device *dev,
return 0;
}
static void *mergeable_xdp_get_buf(struct virtnet_info *vi,
struct receive_queue *rq,
struct bpf_prog *xdp_prog,
void *ctx,
unsigned int *frame_sz,
int *num_buf,
struct page **page,
int offset,
unsigned int *len,
struct virtio_net_hdr_mrg_rxbuf *hdr)
{
unsigned int truesize = mergeable_ctx_to_truesize(ctx);
unsigned int headroom = mergeable_ctx_to_headroom(ctx);
struct page *xdp_page;
unsigned int xdp_room;
/* Transient failure which in theory could occur if
* in-flight packets from before XDP was enabled reach
* the receive path after XDP is loaded.
*/
if (unlikely(hdr->hdr.gso_type))
return NULL;
/* Now XDP core assumes frag size is PAGE_SIZE, but buffers
* with headroom may add hole in truesize, which
* make their length exceed PAGE_SIZE. So we disabled the
* hole mechanism for xdp. See add_recvbuf_mergeable().
*/
*frame_sz = truesize;
/* This happens when headroom is not enough because
* of the buffer was prefilled before XDP is set.
* This should only happen for the first several packets.
* In fact, vq reset can be used here to help us clean up
* the prefilled buffers, but many existing devices do not
* support it, and we don't want to bother users who are
* using xdp normally.
*/
if (!xdp_prog->aux->xdp_has_frags &&
(*num_buf > 1 || headroom < virtnet_get_headroom(vi))) {
/* linearize data for XDP */
xdp_page = xdp_linearize_page(rq, num_buf,
*page, offset,
VIRTIO_XDP_HEADROOM,
len);
*frame_sz = PAGE_SIZE;
if (!xdp_page)
return NULL;
offset = VIRTIO_XDP_HEADROOM;
put_page(*page);
*page = xdp_page;
} else if (unlikely(headroom < virtnet_get_headroom(vi))) {
xdp_room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM +
sizeof(struct skb_shared_info));
if (*len + xdp_room > PAGE_SIZE)
return NULL;
xdp_page = alloc_page(GFP_ATOMIC);
if (!xdp_page)
return NULL;
memcpy(page_address(xdp_page) + VIRTIO_XDP_HEADROOM,
page_address(*page) + offset, *len);
*frame_sz = PAGE_SIZE;
offset = VIRTIO_XDP_HEADROOM;
put_page(*page);
*page = xdp_page;
}
return page_address(*page) + offset;
}
static struct sk_buff *receive_mergeable(struct net_device *dev,
struct virtnet_info *vi,
struct receive_queue *rq,
@ -1185,7 +1260,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
unsigned int headroom = mergeable_ctx_to_headroom(ctx);
unsigned int tailroom = headroom ? sizeof(struct skb_shared_info) : 0;
unsigned int room = SKB_DATA_ALIGN(headroom + tailroom);
unsigned int frame_sz, xdp_room;
unsigned int frame_sz;
int err;
head_skb = NULL;
@ -1215,63 +1290,11 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
u32 act;
int i;
/* Transient failure which in theory could occur if
* in-flight packets from before XDP was enabled reach
* the receive path after XDP is loaded.
*/
if (unlikely(hdr->hdr.gso_type))
data = mergeable_xdp_get_buf(vi, rq, xdp_prog, ctx, &frame_sz,
&num_buf, &page, offset, &len, hdr);
if (unlikely(!data))
goto err_xdp;
/* Now XDP core assumes frag size is PAGE_SIZE, but buffers
* with headroom may add hole in truesize, which
* make their length exceed PAGE_SIZE. So we disabled the
* hole mechanism for xdp. See add_recvbuf_mergeable().
*/
frame_sz = truesize;
/* This happens when headroom is not enough because
* of the buffer was prefilled before XDP is set.
* This should only happen for the first several packets.
* In fact, vq reset can be used here to help us clean up
* the prefilled buffers, but many existing devices do not
* support it, and we don't want to bother users who are
* using xdp normally.
*/
if (!xdp_prog->aux->xdp_has_frags &&
(num_buf > 1 || headroom < virtnet_get_headroom(vi))) {
/* linearize data for XDP */
xdp_page = xdp_linearize_page(rq, &num_buf,
page, offset,
VIRTIO_XDP_HEADROOM,
&len);
frame_sz = PAGE_SIZE;
if (!xdp_page)
goto err_xdp;
offset = VIRTIO_XDP_HEADROOM;
put_page(page);
page = xdp_page;
} else if (unlikely(headroom < virtnet_get_headroom(vi))) {
xdp_room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM +
sizeof(struct skb_shared_info));
if (len + xdp_room > PAGE_SIZE)
goto err_xdp;
xdp_page = alloc_page(GFP_ATOMIC);
if (!xdp_page)
goto err_xdp;
memcpy(page_address(xdp_page) + VIRTIO_XDP_HEADROOM,
page_address(page) + offset, len);
frame_sz = PAGE_SIZE;
offset = VIRTIO_XDP_HEADROOM;
put_page(page);
page = xdp_page;
}
data = page_address(page) + offset;
err = virtnet_build_xdp_buff_mrg(dev, vi, rq, &xdp, data, len, frame_sz,
&num_buf, &xdp_frags_truesz, stats);
if (unlikely(err))